1. Field of the Invention
The present invention relates generally to transmissions which are used in industrial vehicles, such as tractors and forklifts, or in motorized machines, to transmit power to drive wheels and, more particularly, to a transmission, in which an electric or hydraulic motor provided to each drive wheel is coupled to a drive means through a power transmission system having a braking device combined with a planetary gear assembly.
2. Description of the Related Art
Generally, industrial vehicles such as forklifts use a braking device (for example, a disk brake), which is integrated with each power transmission reduction gear system (for example, a planetary gear assembly), in place of using an individual brake integrated with each wheel. In this case, the manufacturing costs are markedly reduced, and the construction of the entire drive/braking system is simplified.
However, in the conventional techniques having the above-mentioned construction, in the case that the braking device is combined with the power transmission reduction gear system, when maintenance or repair work, such as work for repairing an oil lubrication disk of the braking device, is required, it is difficult to disassemble the braking device, because the entire power transmission reduction gear system must be disassembled to access the braking device.
Meanwhile, a representative transmission, which overcomes the above-mentioned problem, in which the entire power transmission reduction gear system must be disassembled in order to access the braking device, was proposed in Europe Patent No. EP 0919416 B1. This transmission will be explained herein below.
The transmission T is coupled at an end thereof to a drive shaft 2 of a drive motor M and coupled at the opposite end thereof to a drive means, such as a wheel or a rotating member R. The transmission T has a structure such that a power transmission path is configured in a “Z” shape through a drive pinion 31. The drive pinion 31 is keyed to the drive shaft 2 of the drive motor M on a drive axis line (X-X).
The drive pinion 31 engages with a driven wheel 32, and a driven shaft 321 is coupled to the center of the driven wheel 32. The driven shaft 321 is disposed on a driven axis line (Y-Y) parallel to the drive axis line (X-X). A first end of the driven shaft 321 is coupled to a fastening member 326 for holding the drive means R. A planetary gear assembly (323 and 325) is coupled to the driven shaft 321 at a predetermined position between the driven wheel 32 and the fastening member 326. The driven shaft 321 is coaxially coupled at a second end thereof to a braking device DF. The braking device DF is placed in a separate chamber attached to the transmission T. The chamber has an opening and an access cover 131. The opening and the access cover 131 are disposed at positions adjacent to the drive motor, that is, at positions opposite the drive means.
In the transmission having the above-mentioned construction, work of modulating or repairing the braking device can be easily conducted by opening the access cover without disassembling the entire power transmission reduction gear system.
However, in the case of this transmission, because the opening and the access cover are disposed opposite the drive means, when it is necessary to disassemble the reduction gear system, parts of the transmission from the drive means to the power transmission part (the drive motor) must be disassembled.
Furthermore, this conventional transmission is problematic in that, due to wear of brake disks of the braking device, the oil for the reduction gear system is deteriorated and the lifetime of the bearings and gears is reduced.